Electrical control circuit and device therefor



ELECTRICAL CONTROL CIRCUIT AND DEVICE THEREFOR Filed Nov. 24, 1937 jfiiz Knee/00A Patented Apr. 2, 1940 UNITED STATES PATENT OFFICE ELECTRICAL CONTROL CIRCUIT AND DEVICE THEREFOR John H. Wheelock, Fitzwilliam, N. H., assignor to Signal Engineering & Manufacturing Com-' pany, New York, N. Y., a. corporation of Massachusetts Application November 24, 1937, Serial No. 176,307

9 Claims. (01. 175-475) C The present invention relates to electrical conenergized position of Fig. 1. The latch pro trol circuits and devices, and relates particularly vides an extension 8 overhanging the pivot 6 to to an improved arrangement for controlling the such an extent that when the armature 4 is operation of electrical apparatus having a relaraised due to full energization of the winding 2,

5 tively heavy current consumption, by means of the entire latch turns in a counterclockwise di- 5 control devices working in a circuit in which reotion to engage a second notch 9 with the end the current consumption is reduced to a miniof the armature 4. Hence, subsequent deenergimum. zation of the winding 2, with the latch in the The circuit and devices of the present invenposition of Fig, 2, has no effect on the armature 10 ti are articularly adapted for use in connec- 4 which remains latched in its raised position. 10 tion with control apparatus employing extremely The overhanging portion 8 of the latch 5 is sensitive electrical contacts of low current carassociated with a solenoid or trip ce l It) having rying capacity. For example, relatively slight a magnetic plunger H movable therein- With movements of a thermo-responsive element may he trip coil I0 in its normal deenergized condibe employed, in accordance with the invention, tion the plunger H rests against a s p i2 W t to perform desired functions through making or on y a po t of the p Within t p e011, breaking an electrical circuit, with complete so that energization of the coil ID will draw the elimination of arcing at the thermo-responsive P e ll p y in the direction of the latch element itself, since all control circuits carrying p r ion any appreciable current are broken at points en- The core I also carries an auxiliary armature 20 tirely removed from the element. Theabove and I3 pivoted at la, the armature I3 overhanging other advantageous features of the invention will the Winding 2 and terminating in a b v d edge hereinafter more fully appear from the following |3a t s pa a beveled edge On an description considered in connection with the ens on M of the core leg carry the Winding accompanying drawing in hi h; 2. The armature [3 provides a weighted exten- 25 Fig. 1 is a schematic view of a control circuit SlOIl y d t D t 50 that normally, and devices embodying the invention, with the winding 2 in deenergized condition, the

Fig. 2 is a schematic view of the apparatus f downwardly extending portion of the armature Fig. 1, illustrating a different opefating condi- I3 is tilted slightly away from the core extension tion. 14 with an appreciable air gap between the bev- 30 Fig. 3 is a view in side elevation of the control e e su a I311 a 5411- AS Will readily pp device shown in Fig. 1. from consideration of Fig. 3, the gap between the Fig. 4 is a view in front elevation of the device u fa s I3aand is considerably ss t in Fig. 3, with some parts broken away to show he normal air gap between the armature 4 and the construction. the core leg whenthe device is deenergized, and 35 Like reference characters refer to like parts in Since the a e s extremely light in Weight the different figures. and nearly in a condition of balance about its Referring first to Figs. 1 and 3, there will first pivot I a r l v ly ll r e f enersi abe described an illustrative embodiment of a detion of the Winding 2 (illsllfilclent to ve y 40 vice for performing certain essential functions effect on t main'armature i l w v r at- '40 in the control circuit of the present invention, tract e armature l3 and move it into a vertialthough it will be readily understood that the 091 Position, as indicated in dotted lines in control device itself is susceptible of many struc- The free end of the armature extension l5 p tural modifications without departing from the VideS an insulating p which is normally invention. The control device generally comlightly in engagement withiohe a p prises a magnetic core I of U- haped fo m one spaced contacts l6, so that attraction of the arleg of which is surrounded by a'winding 2. The mature l3 will cause these contacts I6 to close, other coreleg provides a pivot 3 for an arma as indicated in dotted lines. The latch 5 provides ture 4 and full energization of the winding 2 is a projecting insulating tip 5a, and with the latch adapted to turn the armature 4 from the position 5 in its non-locking position with respect to the 50 of Fig. 1 to the position of Fig. 2. armature 4, the tip 5a maintains a pair of con- A latch 5 pivoted at 6 is associated with the tacts IT in engagement. Therefore, with the confree end of the armature A the upper end of trol device in deenergized condition, the contacts the latch providing a notch ,1 in which the free I6, controlled by the auxiliary armature l3, are

end of the armature 4 rests when-in the deopen while the contacts ll controlled by the latch 65 5 are closed, and the function of these contacts in the control circuit will shortly appear.

The armature l carries a cross bar l3 which, as best shown in Fig. 4, carries an arm S9 insulated from the bar 58 at 2%. The free end of the arm 59 carries a pair of contacts 2| connected by a bridging member 22 and when the armature 4 is raised, as shown in Fig. 2, the contacts 2i establish a circuit between a pair of spaced contacts 23. The armature also carries an arm 2-3 insulated from the bar 58 and contacts 25 at the end of the 24 are connected by a bridging member 25. These contacts 25 establish a circuit between spaced contacts 2? when the armature 4 is raised, as shown in Fig. 2, and for the purpose of simplifying the wiring connections of the circuit of Fig. l, the arm 24 is shown as extending at right angles to the arm l9.

As previously pointed out, the object of the invention is to provide for the control of the operation of apparatus having a relatively heavy current consumption, with the duration of the flow of current throng: the control circuit itself reduced to a minimum and arcing at the movable actuating elements entirely eliminated. As an illustrative embodiment of the utility of the invention, there is shown in Figs. 1 and 2 its functioning in connection with the control of the operation of an electrical motor M by the limited movement of the very sensitive thermo-respcnsive element '1'. For example, the element T may be part of a thermostat of the character frequently employed in connection with the temperature control of buildings, while the motor may be of the type employed to supply a liquid fuel burner. Generally in such a system, it is required that the motor shall be operated when the temperature falls below a certain predetermined minimum and shall be disconnected when the temperature reaches a predetermined maximum in response to functioning of the heating system.

For the purpose of obtaining the above described results, one terminal of the motor M is connected to a supply main 28 while the other terminal is connected to one of the spaced contacts 23. The other contact 23 is connected to a supply main 29 so that the closure of the contacts 23 by the contacts 21 and bridging member 22 will cause the motor to operate as long as the armature 4 remains in the position of Fig. 2. The thermo-responsive element T is shown diagrammatical Y as being of the type having one end anchored, with a free end adapted to move in opposite directions in accordance with its heating and cooling upon an increase or decrease of temperature. As shown, cooling of the element T causes its free end to move towards stationary contact 38 connected to one of the normally closed contacts ll, while heating of the element T will cause its free end to engage a stationary contact connected to one terminal of the trip coil Ill. The fixed end of the element T is connected through a current limiting resistor 3'2 to the supply main 28.

In considering the operation of the control circuit and devices, let it be assumed that the element T is cooling by reason of being subjected to a decrease in temperature. The free end of the element T is, therefore, moving towards the right, as indicated by the small arrow in Fig. 1, and when it engages the contact 33, a circuit is established to the winding 2 from the supply main 28 through the resistor 32, element T, contact 30 and normally closed contacts H. This results in a current flow which is not sufficient to harm the relatively delicate thermostatic contacts T and 30, nor is it suincient to attract the armature 4-; although it will cause the auxiliary armature 53 to be attracted and close the contacts it, as indicated in dotted lines in Fig. 1. When this occurs, a circuit is established from the supply main 28 through closed contacts It to the closed latch contacts 17 and one terminal 01 the winding and since the other terminal is connected to supply main 23, there results lull energization of the winding 2, the resistor 32 and thermostatic contacts T and 3E then being shunted out through contacts [6.

The armature 4 thereupon pulls up, as shown in Fig. 2, and as the free end of the armature leaves the notch l on the latch 5, the latter turns about its pivot 6 into a substantially vertical position with the upper notch 9 receiving the end of the armature. Closure of the armature 4 and functioning of the latch 5 bring about a number of changes in the control circuits which will be described in the order of their occurrence. In the first place, closure of the motor contacts 23 by the bridging contacts 2i as the armature pulls up, starts the motor M and the motor will continue to operate directly across the mains 28 and 29 as long as the armature 4 remains locked up. However, the winding 2 is completely deencrgized almost immediately after the armature 4 pulls up due to the fact that as the latch 5 drops to the armature locking position, the contacts I! are opened by upward movement of the tip 5a, there by breaking the circuit of the winding 2 even though at that moment the contacts l6 are still closed by reason of the attraction of the auxiliary armature IS. The control circuit is, therefore. in the condition of Fig. 2 almost immediately after the armature 4 is locked up by the latch 5 and obviously when the element T starts to move towards the left in response to a rise in temperature due to continued operation of the motor M, there can be no arcing at the contact 39 due to the fact that the circuit originally established from the main 28 through the contact 3!] has previously been broken by opening of the latch contacts l7.

Looking up of the armature 4 also accomplishes another result. namely, the closure of a portion of the circuit of th trip coil H) in advance of completion of that circuit when the thcrmo-rcsponsive element T engages the contact 3|. As previously pointed out, the arm 24 on the armature 4 carries bridging contacts 25 and these contacts establish a circuit between the stationary contacts 2'! when the armature is locked up, thereby connecting the upper terminal of the trip coil ill to the supply main 29. Therefore, when continued movement of the free end of the element T to the left, due to its heating, results in engagement with the contact 3!, a circuit is established through the trip coil l8, due to the previous closure of the contacts 21. Trip coil Ill is so designed that the current flow through this circuit is of the same order as that through the contact 38, and the resulting upward movemen of the plunger engages the latch extension 8 and turns it about its pivot to the dotted line position of 2.

Upon release of the free end of the armature 4 from the upper notch 9, the armature 4 drops to the full line position of Fig. 1, thereby immediately stopping the motor M due to the opening of contacts 23. At the same time opening of contacts 21 through movement of the arm 24 deenergizes the trip fcoil l0, so-that the plunger H returns to its deenergized position. However, the latch cannot fall back owing to the fact that the free end of the armature 4 is then received in the lower notch 1, thereby leaving the latch in an unbalanced condition ready to perform its function of latching up the armature upon the next full energization of the winding 2. Obviously, opening of the contacts 21 in ci'r-- cuit with the trip coil l0 eliminates any possibility of arcing at the contact 3|, when the element T in response to a decreasing temperature, following stoppage of the motor M, starts to move to the right and leave the contact 3|.

The above described cycle of operation will continue indefinitely in response to temperature changes to which the element T is subjected without any possibility of injurious arcing ever occurring between the sensitive contacts 30 and 3| and the element-T itself. This is a most important feature of the invention since it is well known that many thermostatic devices fail to function properly after being in service for any considerable time due to deterioration of electrical contacts in the device itself by arcing. Furthermore, it is to be noted that the main winding 2 and the trip coil are only momentarily energized in response to the functioning of the non-arcing element T. When suflicient current is passed through the winding 2 to cause the armature 4 to pull up, the circuit is almost immediately broken at the latch controlled contacts 11, while the trip coil circuit is broken immediately after release of the latch unlocks the armature 4 and opens the contacts 21. Therefore, even though relatively long periods of time may elapse between engagement of the element T with the contacts 30 and 3|, no part of the control circuit and associated devices is being traversed by a continuously maintained current. This reduces the current consumption of the control circuit and associated devices to an absolute minimum, thereby greatly increasing the reliability of the control arrangement as a whole.

I claim:

1. In an electrical control circuit, a source of electrical energy, a current consuming device having one terminal thereof connected to one side of said source, a control element having one terminal thereof connected to the other side of said source and movable to complete a circuit through said current consuming device, means in circuit with said element for restricting the flow of current through said device to a low initial value, means responsive to energization of said device at said initial current value for increasing the flow of current through said device, independently of said element, and means responsive to the increased current flow through said device alone, to interrupt the flow of current through said element.

2. In an electrical control circuit, a source of electrical energy, a current consuming device having one terminal thereof connected to one side of said source, a control element having one terminal thereof connected to the other side of said source and movable to complete a circuit through said current consuming device, means in circuit with said element for restricting the flow of current through said device to a low initial value, means responsive to energization of said device at said initial current value for increasing the flow of current through said device and means responsive to the increased current flow through said device alone to automatically interrupt the flowof current through said device and said con;- trol element while the latter remains stationary.

'3. In an electrical control circuit, a source of electrical energy, an operating winding having one terminal thereof connected to said source, a control element having one terminal thereof connected to the other side of said source and movable to complete a circuit through said winding, means in circuit with said element for restricting the flow of current through said winding to a low value, means responsive to the initial energization of said winding through said element, and controlled by said winding, to increase the flow of current through said winding independently of said element, and means responsive to the increased energization of said winding alone to interrupt automatically the flow of current through said element.

4. In an electrical control circuit, a source of I electrical energy, an operating winding having one terminal thereof connected to said source, a control element having one terminal thereof connectedlto'the other side of said source and movable to complete a circuit through said winding, meansv in. circuit with said element for restricting the flow of current through said winding to a'low value, means responsive to the initial energization of said winding through said element, and controlled by said winding, to increase the flow of current through said winding independently of said element, and means responsive to the increased energization of said winding alone to interrupt automatically the fiow of current through said winding and said control element while the latter remains stationary.

5. In an electrical control circuit, a source of electrical energy, a circuit controlling device comprising a winding, having one terminal connected to said source, a control element having one terminal thereof connected to the other side of said source, a stationary contact engageable by movement of said element and connected to the other terminal of said winding, engagement of said element with said contact serving to cause initial energization of said winding at a low current value, means for causing increased energization of said winding, independently of said control element, and means responsive to increased energization of said winding to interrupt the flow of current through said element and contact.

6. In an electrical control circuit, a source of electrical energy, a circuit controlling device comprising a winding having one terminal connected to said source, a control element having one terminal thereof connected to one side of said source, a stationary contact engageable by said element for completing the circuit through said winding, current limiting means for restricting the flow of current through said element and winding to a small initial value, means controlled by the initial current flow through said winding for increasing the current through said winding alone and means responsive to increased energization of said winding to interrupt the flow of current through both said element and said winding, while said control element remains in engagement with said contact.

7. In an electrical control circuit, a source of electrical energy, a circuit controlling device comprising a winding having one terminal thereof connected to one side of said source, a magnetic member responsive to energization of said winding at a given current value, a control element having one terminal thereof connected to the other side of said source and movable to complcte a circuit through said winding to energize the same at a current value lower than said firstnamed current value, means responsive to initial energization of said winding at the lower current value to increase the current flow therethrough and cause it to attract said magnetic member, means responsive to attraction of said magnetic member to break the circuit between said control element and said winding, while said element remains stationary, and means to maintain said magnetic member in its attracted position, after the flow of current through said winding has been interrupted.

S. In an electrical control circuit, a source of electrical energy, a winding having'one terminal thereoiconnected to one side of said source, a second Winding normally having both terminals unconnected to said source, a movable control element having one terminal thereof connected to the other side of said source and a pair of stationary contacts engageable by said element, with each contact connected to a terminal of one of said windings, movement of said element in one direction to engage one contact serving to cause initial energization of the first-named winding through connection of its other terminal to said source through said element, and means responsive to initial energization of said source-connected winding to automatically interrupt the now of current from said element-engaged contact to said winding and to connect one terminal of said second-named winding to said source, in advance of engagement of said element with said other stationary contact.

9. In an electrical control circuit, a source of electrical energy, a winding having one terminal thereof connected to one side of said source, a second winding normally having both terminals unconnected to said source, a movable control element having one terminal thereof connected to the other side of said source and a pair of stationary contacts engageable by said element, with each contact connected to a terminal of one of said windings, movement of said element in one direction to engage one contact serving to cause initial energization of the first-named winding through connection of its other terminal to said source through said element, and means responsive to initial energization of said sourceconnected winding to automatically interrupt the flow of current from said element-engaged contact to said winding and to connect one terminal of said second-named winding to said source, with further movement of said element in the opposite direction to engage the other of said contacts serving to energize the second-named winding, and means responsive to energization of said second-named winding for restoring the previously broken circuit between said first-named winding and said contact.

JOHN H. WHEELOCK. 

